The present invention generally relates to medical imaging. In particular, the present invention relates to systems and methods for an interactive picture archiving and communication system (PACS) image display test image.
PACS connect to medical diagnostic imaging devices and employ an acquisition gateway (between the acquisition device and the PACS), storage and archiving units, display and review workstations, databases, and sophisticated data processors. These components are integrated together by a communication network and data management system. A PACS has, in general, the overall goals of streamlining health-care operations, facilitating distributed remote examination and diagnosis, and improving patient care.
A typical application of a PACS system is to provide one or more medical images for examination by a medical professional. For example, a PACS system can provide a series of x-ray images to a display workstation where the images are displayed for a radiologist to perform a diagnostic examination. Based on the presentation of these images, the radiologist can provide a diagnosis. For example, the radiologist can diagnose a tumor or lesion in x-ray images of a patient's lungs. Thus, it is highly desirable that the digital images be correctly displayed.
Acquisition modalities, such as digital x-ray (DX), computed tomography (CT), and magnetic resonance (MR), may be configured in various ways to send images to the PACS. For example, different modalities from different vendors may use different send and/or transfer orders and/or different image formats. In addition, PACS and review workstations may be configured in various ways to receive and display images. For example, the PACS workstation may be configured to display images according to a set of hanging protocol rules that control image appearance.
A common format used for medical images is the Digital Imaging and Communications in Medicine (DICOM) format. The DICOM format consists of two aspects, the image pixel data and the DICOM header tag elements. DICOM images often contain look-up tables (LUTs) that are used to display medical images. The LUTs may be applied to the image pixel data and/or in the header tag elements of a DICOM image. The LUT may be used to provide a mapping from an image pixel value to a display brightness. That is, a LUT may affect the way an image is displayed.
PACS and review workstations often fail to display medical images correctly. For example, they may not apply a LUT included in the DICOM header; display or use incorrect brightness and/or contrast values; apply a separately unspecified LUT; apply a LUT incorrectly; apply a LUT, but may not interactively update the image display when the user changes the brightness and/or contrast; not offer options of which LUT to display if multiple LUTs are included; not allow the user to view DICOM header information; and/or have unintended interactions in the image display based on collimation, annotations, or other image features.
A common cause of difficulties with image display on PACS workstations is that the DICOM rules are not clearly defined and may be interpreted in different ways. For example, the DICOM rules for the value-of-interest LUT (VOI-LUT) do not clearly state how a PACS should respond when a user changes brightness or contrast.
Another cause of difficulties is that many DICOM formats exist, such as DX, CT, and MR. In addition, there are many medical imaging modality vendors and many medical imaging PACS and review workstation vendors. Combined with the number of aspects and features of image display, the possible opportunities for defect is on the order of 10,000-1,000,000. Thus, it is difficult to create one comprehensive tool to evaluate the multifaceted nature of testing image display. However, it is highly desirable that a PACS correctly display each modality and each type of LUT, such as VOI-LUT, modality LUT, etc.
As previously mentioned, it is highly desirable to display medical images correctly. Thus, it is useful to know the features and/or behaviors of particular modalities and image display systems. For example, if a particular image display system claims to support a particular LUT, but actually does not implement it as expected by the modality, it may be desirable to detect the actual behavior of the image display system and configure the modality's behavior based on that behavior. As another example, an image display system may not implement a particular feature, and thus it may be desirable to configure the modality to provide images in a different manner to account for the lack of the feature in the image display system.
Current modalities, PACS, and review workstations may provide one or more test patterns. Two common test patterns are the 1985 SMPTE test pattern and the AAPM Task Group (TG) 18 test patterns. These patterns were initially designed for physics evaluations of image display devices, such as monitors.
The SMPTE pattern is often used in the medical imaging field. For example, the SMPTE pattern is included with many current acquisition modalities and image display systems. The SMPTE pattern does not include a LUT. Thus, the SMPTE pattern cannot test aspects of image display relating to LUTs.
The AAPM TG-18 test patterns include many different patterns and clinical images. Each image is a completely separate file from the others. In addition, the TG-18 test patterns do not combine clinical sample images with test patterns. Similar to the SMPTE pattern, the TG-18 test patterns do not include or test LUTs. Further, neither the SMPTE pattern nor the TG-18 pattern was designed for testing clinically relevant image display functionality.
Other standards exist for display monitor evaluation including, for example, the NEMA-DICOM standard part 3.14, the German DIN standard, the ISO 9241 and 13406 series, and the VESA standard. However, these standards focus on monitor evaluation through static, single test patterns. They do not evaluate image display functionality related to PACS and review workstations.
IHE and DICOM Working Group (WG) 11 also provide a series of publications and images that offer functionality and methodology for image display consistency testing. This set of test image patterns provides a series of images to evaluate various LUT combinations (Modality LUT, VOI LUT, and Presentation LUTs); a series of images to evaluate the impact of non-grayscale variations (annotations, shuttering, and spatial transformations); a series of images to evaluate softcopy-to-softcopy consistency, softcopy-to-hardcopy consistency, and hardcopy-to-softcopy consistency; and a test pattern that combines a ramp pattern with a luminance square that can be measured.
However, the IHE test images do not provide a combination of test pattern with a clinical sample image providing simultaneous evaluation of luminance saturation and clinical image display. In addition, the IHE test images do not allow for quantitative comparison of two images for relative comparisons, provide universality of image pixel data, provide a method to test the interactive nature of image display when a user changes the brightness or contrast, or provide asymmetry in the VOI-LUT that helps evaluate whether the LUT is applied correctly.
Thus, there is a need for systems and methods for an interactive PACS image display test image.